测试输入的字符是不是为0-9的数字

测试输入的字符是否为0-9的数字

public static boolean isNum(String str)

{

          boolean flag=true;

          if(str.length()==0)

           flag=false;

         char[] ch=str.toCharArrary();

         for( int i=0; i<ch.length;i++)

        {

                                if(ch[i] < ' 0 ' || char[i] > ' 9 ')

                                                {

                            flag=false;

                             break;

                        }

         }

               return flag;   

}